This study retrospectively investigated the developmental perspective of 69 children (40 males, 29 females) with‘potentially simple’congenital disorders of the peripheral visual system: development was examined in the context of degree of visual impairment. Developmental and visual assessments were carried out at 10 to 16 months (Time 1) and 27 to 54 months of age (Time 2). Participants were grouped according to (1) visual status: profound visual impairment (PVI), severe visual impairment (SVI); (2) developmental status on the Reynell‐Zinkin scales. A majority of the sample showed normal development on all subscales (62% Time 1, 57% Time 2). Those with PVI were more developmentally vulnerable than SVI with a greater incidence of (1) uneven developmental profile at Time 1 (48% PVI, 16% SVI); (2) global learning difficulties at Time 2 (37% PVI, 0% SVI); (3) delay on individual subscales at Time 2 (p<0.02 PVI versus SVI); (4) deceleration (verbal comprehension 74% PVI, 24% SVI, sensorimotor understanding 70% PVI, 27% SVI); and (5) severe developmental setback (33% PVI, 7% SVI). Risk factors of visual level, age, and sex for poor developmental outcome in infants with visual impairment were established.

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IntroductionThis review draws together current understanding of the impact of visual impairment (VI) on early neurodevelopmental and neurobiological processes. The impact is recognized as being substantial. Two major problems make it difficult to draw conclusions from much of the literature on this subject. The first is the heterogeneity of samples of children with VI in terms of additional impairments that introduce multiple confounding variables: in Western societies the prevalence of additional impairments is 60 to 70%. 1-3 Secondly, subgrouping according to the degree or severity of VI is inconsistent and can be suboptimal for developmental studies of infancy. Our group has reconsidered these questions of taxonomy and applied new ones to our recent research cohorts.Below we describe our research/service teams and clinic population, define the new taxonomies, and discuss the influences of VI on, and interactions between the visual, psychological, psychosocial, neurological, and genetic domains. Within the diagnostic category with the fewest confounding variables we identify a subgroup with an unfavourable outcome: those with a developmental setback. We debate how this subgroup might inform our understanding, not only of the impact of VI on neurodevelopmental processes but also of the mechanisms underlying the genesis of regressive disorders in those with VI and in the sighted. These issues are discussed in the context of research of our own and other groups and of current theory. Potential avenues for future investigation are put forward in each section.

The childhood condition of visual difficulties caused by brain damage, commonly termed cortical or cerebral visual impairment (CVI), is well established but has no internationally accepted definition. Clarification of its core features is required to advance research and clinical practice. This systematic review aimed to identify the definitions of childhood CVI in the original scientific literature to describe and critically appraise a consensual definition of the condition. MEDLINE, EMBASE, PsychINFO, CINAHL and AMED databases were searched in January 2017. Studies were included if they (1) were published original research, (2) contained a childhood CVI sample, (3) contained a definition of CVI and (4) described their CVI identification/diagnostic method. Thematic analysis identified concepts within definitions and narrative synthesis was conducted. Of 1150 articles, 51 met inclusion criteria. Definitions were subdivided according to detail (descriptive definition, description not reaching definition status and diagnostic/operationalising criteria). Three themes concerning visual deficits, eye health and brain integrity were identified (each containing subthemes) and analysed individually across definitions. The most common themes were visual impairment' (n=20), 'retrochiasmatic pathway damage'(n=13) and 'normal/near normal eye health' (n=15). The most consensual definition identified here may not be the best quality for advancing our understanding of CVI. We argue for the alternative definition: verifiable visual dysfunction which cannot be attributed to disorders of the anterior visual pathways or any potentially co-occurring ocular impairment. We propose reporting guidelines to permit comparison across studies and increase the evidence base for more reliable clinical assessment and diagnosis.

RESULTS A total of 45 females and 38 males (mean age 3y 5mo; range 10mo-6y 10mo) with ONH or SOD and profound visual impairment (PVI) or severe visual impairment (SVI) were assessed. A total of 58% of children had at least one SCRR difficulty, and 31% had a clinical diagnosis of ASD. The prevalence of ASD was slightly higher in children with SOD than in children with ONH (36% vs 26%) also slightly more frequent in children with PVI than in children with SVI (36% vs 27%). The prevalence of SCRR difficulties was statistically higher in children with PVI than in children with SVI (p=0.003). Clinical ASD was most likely to be diagnosed between 2 years 4 months and 4 years 6 months. Development was significantly delayed in children with ASD compared with children without social communication difficulties (p=0.001).

This study retrospectively investigated the developmental perspective of 69 children (40 males, 29 females) with 'potentially simple' congenital disorders of the peripheral visual system: development was examined in the context of degree of visual impairment. Developmental and visual assessments were carried out at 10 to 16 months (Time 1) and 27 to 54 months of age (Time 2). Participants were grouped according to (1) visual status: profound visual impairment (PVI), severe visual impairment (SVI); (2) developmental status on the Reynell-Zinkin scales. A majority of the sample showed normal development on all subscales (62% Time 1, 57% Time 2). Those with PVI were more developmentally vulnerable than SVI with a greater incidence of (1) uneven developmental profile at Time 1 (48% PVI, 16% SVI); (2) global learning difficulties at Time 2 (37% PVI, 0% SVI); (3) delay on individual subscales at Time 2 (p<0.02 PVI versus SVI); (4) deceleration (verbal comprehension 74% PVI, 24% SVI, sensorimotor understanding 70% PVI, 27% SVI); and (5) severe developmental setback (33% PVI, 7% SVI). Risk factors of visual level, age, and sex for poor developmental outcome in infants with visual impairment were established.

Lack of vision is associated with delayed early-object manipulative abilities and concepts; 'form' vision appeared to support early developmental advance. This paper provides baseline characteristics for cross-sectional and longitudinal follow-up investigations in progress. A methodological strength of the study was the representativeness of the cohort according to national epidemiological and population census data.

The future direction for service delivery and evaluation is briefly described.